1. Field of the Invention
The present invention relates to a magnetic head suspension for supporting a magnetic head slider that reads and/or writes data from and to a recording medium such as a hard disk drive.
2. Related Art
In recent years, data storage devices for reading and/or writing data from and to recording mediums through a magnetic head slider have been widely used in mobile devices such as notebook-type personal computers and portable music players and, along therewith, these data storage devices have been required to have a higher impact resistance.
More specifically, in such a case where the data storage device in operation is dropped on to the ground, the magnetic head suspension is desired to prevent the magnetic head slider from damaging a disk surface as much as possible.
For example, in a case where the data storage device in operation is applied with an impact force having such a direction that presses the magnetic head slider toward the disk surface, an air film existing between the magnetic head slider and the disk surface prevents to some extent the magnetic head slider from hitting the disk surface.
However, on the other hand, in a case where the data storage device in operation is applied with an impact force having such a direction that presses the magnetic head slider away from the disk surface and having a strength exceeding a predetermined level, the magnetic head slider jumps away from the disk surface and then swings back to hit the disk surface, which will result in damages to the disk surface as well as to the magnetic head slider.
Accordingly, in order to improve the impact resistance of the data storage device, it is required to prevent the jumping motion of the magnetic head slider as much as possible when the impact force is applied from the outside, that is, it is required to raise as much as possible acceleration (critical acceleration) of the impact force that causes the jumping motion of the magnetic head slider.
The magnetic head slider is supported by the magnetic head suspension that is mounted to the data storage device.
More specifically, the magnetic head suspension includes a load bending part that generates a load to press the magnetic head slider toward the disk surface, a load beam part that transmits the load to the magnetic head slider, a supporting part that supports the load beam part with the load bending part interposed between the supporting part and the load beam part, and a flexure part that has a head-mounting region to which the magnetic head slider is mounted and that is welded to the load beam part.
The critical acceleration can be increased by, for example, increasing the load that is generated by the load bending part.
However, the load needs to be set within a range appropriate for controlling the height by which the magnetic head slider flies above the disk surface. Accordingly, there is obviously a limitation in the method of increasing the load to increase the critical acceleration.
It is also possible to increase the critical acceleration by reduction in weight of the load beam part so as to reduce an inertial force that is applied to the load beam part upon application of an impact force.
However, such reduction in weight of the load beam part requires reduction in thickness of the load beam part or provision of a hole in the load beam part, which will result in deterioration in rigidity of the load beam part and therefore deterioration in vibration property as well as in load/unload property.
There has been proposed still another configuration to inhibit the jumping motion of the magnetic head slider upon application of an impact force. In such a configuration, the load beam part is provided with an extension portion that extends toward a base end beyond a portion joined to the load bending part (refer to Japanese Unexamined Patent Publications Nos. 09-082052, 11-039808, 2004-348804, 2005-174506, and the like).
The conventional structure described in these the patent documents is configured so as to make a mass of a portion of the load beam part which is positioned on a base-end side in a suspension lengthwise direction from the load bending part to be as equal as possible to a mass of a portion thereof which is positioned on a tip-end side of the suspension lengthwise direction from the load bending part so that the jumping motion of the magnetic head slider is suppressed at a time when the external impulsive force is applied. The structure is advantageous in causing no deterioration in rigidity of the load beam part.
However, in the magnetic head suspension described in these patent documents, the load beam part is joined to a free end of the load bending part that is supported by the supporting part in a cantilevered manner. Accordingly, in this configuration, a support point of the load bending part (that is, a joint point between the load beam part and the load bending part) is remarkably fluctuated in a direction perpendicular to the disk surface upon application of an external impact force.
Therefore, although the magnetic head suspension described in these patent documents does not cause deterioration in rigidity of the load beam part, it is incapable of allowing the critical acceleration to be sufficiently increased.
The magnetic head suspension is a member that rapidly moves the magnetic head slider in a radial direction (a seek direction) above the recording medium such as a hard disk in accordance with driving of an actuator so as to accurately position the magnetic head slider on a target track. Thus, the magnetic head suspension is also desired to accurately control its vibration property, particularly a vibration property in the seek direction in parallel with the disk surface.
More specifically, the magnetic head suspension needs to have a resonant frequency in the SWAY mode that is equal to none of the resonant frequencies of the magnetic head suspension in any other modes and the resonant frequencies of any components of the data storage device other than the suspension.
Furthermore, the magnetic head suspension is desired to effectively prevent or reduce displacement of the magnetic head slider in the seek direction due to vibration of the magnetic head suspension in the torsion mode.